to pay tribute to america's heroes, nasa honoring today u.s. astronauts who have died in the line of duty including the crews of space shuttles challenger and columbia. today's ceremonies marking a day of remembrance ten years after the columbia accident. steve harrigan is live in cape canaveral, florida. steve? >> reporter: jon, a day of remembrance here, but also a day of gratitude, remembering those who gawf their lives for -- gave their lives for space exploration. among the speakers, the widow of the commander of the spaceship columbia. >> february 1, 2003, became a traumatic, shocking day. anticipating a joyful homecoming of our crew, we were jolted in the viewing area into a nightmarish stroll of fear, uncertainty and horror. that led to a crushing announcement that the crew had perished. >> reporter: three major tragedies in nasa's history claimed the lives of 17 astronauts beginning in 1967 with the apollo i, a fire onboard the capsule on the launching pad claimed the lives of three including gus brisesome, a veteran of the america ri